Ethics Chairwoman Zoe Lofgren (D-Calif.) and ranking member Jo Bonner (R-Ala.) did not specify the allegations involving each lawmaker, but all six have been identified in reports in the Wall Street Journal regarding their use of cash stipends for overseas travel.

The investigation was referred to the ethics panel by the Office of Congressional Ethics, the quasi-independent House agency tasked with reviewing potential rules violations and recommending formal investigations.

The ethics committee will announce whether to pursue the matter by Dec. 20, the statement said.

The Wall Street Journal had reported earlier this year that Members of Congress routinely pocketed per diems that were provided for their official travel expenses abroad.